In a large pot, heat oil over medium-low heat. Trim the root ends of the scallions and chop. Add the light green part of scallions to pot with garlic and ginger. Cook 2-3 minutes. Reserve the dark green scallion parts for topping. Add the broth and bring to a boil, reduce to a simmer, and cook 5 minutes.

While the broth is simmering, cut bok choy, separating stems from greens. Cut both stems and greens into thin strips. Add stems to pot and cook for 5 minutes, or until they start to be tender. Add the leaves and cook 5 minutes more. Add the ramen and simmer until noodles and bok choy are tender, about 4 to 6 minutes. Taste and add salt if needed.

Divide into two bowls and top with scallion greens, sesame seeds, and red pepper flakes.